Experimental and numerical damage analysis of composite patched AA2024-T3 plates with notch and adhesive void defects

In bonded repair of damaged structures, it is essential to ensure efficient load transfer without affecting the integrity of the adhesive layer, which is typically the weakest component of the repaired structure. However, other factors can significantly affect the bonded repairs performance, particularly the aging and bonding defect effects, because these factors negatively affect the integrity of the adhesive layer and, consequently, the overall effectiveness of the repair. The present work is carried out within this context and aims to investigate the load-elongation response of a damaged structure repaired with a bonded composite patch while considering the presence of defects within the adhesive layer. The numerical analysis is based on the combined use of the Extended Finite Element Method (XFEM) and Cohesive Zone Modeling (CZM) to simulate damage evolution in the aluminum plate and the adhesive layer, respectively. Particular attention is given to the impact of defect size and location within the adhesive layer. The results demonstrate that the presence of adhesive defects compromises the overall strength of the repaired structure, with the severity of the degradation depending on both defect size and location. Defects located around the notch increase stress concentrations within the aluminum plate, whereas defects positioned at the patch edge promote earlier debonding initiation and faster damage propagation by affecting a critical load transfer region.